1. Field of the Invention.
The field of the invention relates to a method for connecting wires, particularly those within high density, flat transmission cables, to multipole connectors, and a crimp type micro-multipole connector for facilitating said method.
2. Brief Description of the Prior Art.
Electrical connections in many applications are made through such commonly known methods such as soldering, spot welding and lapping. In the field of micro-connectors, however, crimp type connections and insulator displacement connections (IDC) are more popular for connecting conductors to electrical connectors. The former method includes the clamping of a crimp barrel formed on the tail portion of a contact member about a conductor. The latter involves the pressing of an insulated wire into an IDC contact member having a U-shaped slot. Crimp connections are mainly used for connecting a single wire to a single crimp type contact member. IDC connections are generally employed in mass type connecting procedures wherein a plurality of conductors in a flat cable or ribbon cable are connected to IDC connectors having appropriately designed contacts therein.
The tendency towards miniaturization of electrical components has made traditional connecting methods less reliable. A high density signal transmission cable may have a plurality of signal conductors (e.g. 24), each having a diameter of about 0.20 mm distributed along 1.27 mm center lines. Grounding wires of about 0.254 mm diameter are provided on both sides of the signal wires and spaced about 0.46 mm therefrom. There is accordingly a space of about 0.35 mm between adjacent grounding wires. In order to connect a plurality of signal wires of such a high density flat cable to the related circuits, various types of 1.27 mm pitch multipole micro-connectors are employed. A plurality of wires in the flat cable may, for example, be simultaneously pressed into IDC contact members in an IDC type connector. If crimp connections are instead employed, a crimp barrel of a contact member is crimped to a conductor of an insulated wire and, thereafter, a plurality of contact members so crimped are successively inserted into the cavities of an insulator or housing. The method using IDC connectors has been preferred because of its simplicity.
The increasing miniaturization of flat cable has limited the ability to successfully employ IDC connectors. Due to the small distances between signal and/or ground wires, the U-shaped slots within IDC contact members must be extremely small to accommodate them. The mechanical strength of these contact portions is greatly reduced making it virtually impossible to use the IDC connecting process for flat cables having wire separation of less than 0.5 mm. In addition, resistance to vibration and tension is impaired as compared to crimp type connections. The resulting reduction in reliability is a fatal defect for this type of application. A connection failure in just one portion of the connector results in the loss of reliability in the connector generally.
While the crimp connection process as described above is technically feasible for miniaturized, high density, flat cables, the process of crimping the wires one by one and then securing the crimped contacts into housings is both difficult and inefficient.
Batch processes involving such crimp connections would also be impractical. Such processes would include utilizing a preassembly housing having a plurality of contact members therein, each contact member having a crimp section. The conductors of the flat cable would be inserted within the crimp sections and the crimp sections compressed simultaneously. It would be very difficult to assure reliable electrical connection at this high rate, however. In addition, the spacing of the comb-shaped teeth of a punch or crimper used for such a micro-connector would be so small that the strength of the crimper would be substantially reduced. Delicate controls would be required for installing the crimper and corresponding anvil and maintaining them during the crimping process.
Current technology does not permit the use of lapping techniques for high density flat cables. Soldering is also unacceptable as it would cause a short circuit between adjacent conductors due to fluctuation of the solder supply.